Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Goes well beyond the annotations: it names the visible side effect (icon on the home screen), enumerates failure codes (unknown_app, already_installed), explains the marketplace-unreachable fallback, and crucially discloses that the install is simulated and logged in device_log. That simulation note is exactly the kind of context annotations cannot express.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Four short sentences, front-loaded with the action, then effects, then failure modes, then the simulation caveat. Every sentence contributes distinct information with no padding.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-parameter mutation tool with no output schema, the description covers side effects, error conditions, and fallback behavior thoroughly. It stops short of describing what a successful call returns, which would have completed the picture.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and both parameters are already documented (id from list_store_apps, session from open_app). The description adds no syntax or format detail beyond that, so the baseline of 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ("Install a Store app on the phone") plus a concrete behavioral analogy ("as tapping Install in the Store screen does"). It does not, however, distinguish itself from the sibling request_app_install, which an agent must choose between.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The Store-screen analogy implies the context (an app must exist in the Store catalog) and the marketplace-unreachable fallback gives a hint about environment. But there is no explicit when-to-use versus request_app_install, uninstall_app, or list_store_apps.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.